Nothing is official yet -- despite what hit the Twitterverse on Wednesday night -- but all signs point to Austin being named Caldwell's defensive coordinator with the Lions. And while much of the Ravens coaching upheaval has affected the offense, Austin's pending departure would create a significant void on the defensive staff.

A new secondary coach would inherit one of the Ravens major developmental projects in safety Matt Elam, whom the Ravens expect to be a cornerstone of the defense for the next few years at least. As a rookie, Elam played out of position much of this season as a free safety, but the Ravens are expected to move Elam to his more natural position of strong safety in 2014.

That leaves a vacancy at free safety, which general manager Ozzie Newsome identified as one of the major needs of this offseason. So any new secondary coach would also be charged with assimilating a new starting free safety into the defense, whether that be a veteran or a rookie draft pick.

The secondary coach has a good group of corners to work with, thanks largely to Austin. Cornerback Jimmy Smith was the Ravens most improved player this season, finally flashing the potential that made him a late first-round draft pick. It's up to his position coach to continue that development.

Austin also helped Cary Williams, Corey Graham and James Ihedigbo all develop from special teams players to starting NFL defensive backs.

Should Austin go to Detroit, one possible in-house candidate to replace him would be Steve Spagnuolo, who spent the past season as a senior defensive assistant with the Ravens. Spagnuolo and Harbaugh worked for several years together in Philadelphia, and Spagnuolo was the Eagles defensive backs coach from 2001-03. Spagnuolo also has past experience as an NFL head coach and defensive coordinator.